The present invention relates generally to wireless communications and more particularly to a method and apparatus for removing a Direct Current Offset Component (DCOC) from a baseband signal in a wireless receiver, such as a Global System for Mobile communication (GSM)/Enhanced Data rate for GSM Evolution (EDGE) receiver.
Very low intermediate (VLIF) receivers used in wireless communication devices typically include a high pass filter (HPF) for removing the DCOC from an intermediate frequency (IF) signal that passes through the receiver component before the IF signal is down converted to a baseband frequency. For example, a GSM/EDGE receiver can include a finite impulse response high pass filter (FIR HPF) that partially removes the DCOC before the IF signal (e.g., a 110 kHz GMSK/8 PSK signal) is down converted to the baseband frequency.
Unfortunately, using a FIR HPF to partially remove the DCOC can cause gain and phase distortion to the IF signal, thus degrading the receiver performance. One approach to improving the performance is to reduce the notch bandwidth of the FIR HPF. However, using a FIR HPF with a smaller notch bandwidth results in longer latency, which extends the receiver set up time making it difficult to support a multi-slot receiver. As such, using a FIR HPF to reduce the DCOC requires a tradeoff between latency and signal quality.
It would be desirable to provide improved techniques for efficiently removing the DCOC from an intermediate frequency (IF) signal before the IF signal is down converted to baseband frequency. It would be particularly desirable if such techniques exhibit low latency, while preserving signal spectrum with minimum gain and phase distortion.
Those of skill in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.